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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 116 |
| 5 | 1560 |
| 6 | 26886 |
| 7 | 565376 |
| 8 | 14036392 |
| 9 | 401823360 |
| 10 | 13030976650 |
| 11 | 472154276352 |
| 12 | 18903994333212 |
| 13 | 828807273828352 |
| 14 | 39491616319733774 |
| 15 | 2032038033784995840 |
| 16 | 112293378446546611280 |
| 17 | 6632975513529162694656 |
| 18 | 417050432063319431036178 |
| 19 | 27809989478829060358799360 |
[1,2,12,116,1560,26886,565376,14036392,401823360, 13030976650,472154276352,18903994333212, 828807273828352,39491616319733774, 2032038033784995840,112293378446546611280, 6632975513529162694656,417050432063319431036178, 27809989478829060358799360] |